1. Field of the Invention
The present invention relates to a hydraulic reservoir and, more particularly, to a hydraulic fluid reservoir formed by rotational molding with an inserted baffle.
2. Brief Description of the Prior Art
Rotational molding, or rotomolding, is a well-known method of forming objects from a plastic resin. It is often used for complex shapes including tanks and reservoirs. Various types of plastic resin can be used, such as polyethylenes, plastisols, nylons, fluoropolymers, polypropylenes, polyurethanes, and other suitable materials.
In general, a mold is loaded with a plastic resin and heated in an oven. As the mold is heated, the mold is rotated about two or three axes at a low speed. The heat melts the plastic resin inside the mold and melted resin coats the interior surface of the mold. The mold is then gradually cooled using air or water and the re-solidified plastic resin, which has assumed the shape of the interior walls of the mold, is removed from the mold. This process differs from injection molding in that the plastic resin is not pressurized (other than atmospheric pressure).
U.S. Pat. No. 5,285,923 illustrates the insertion of objects made of a material other than plastic resin into the object to be formed, such as brass inserts molded into a polyethylene material. In general, the insert is placed in a designated spot in the mold and the rotomolding process is initiated as described above. The melted plastic resin encapsulates the insert and the insert becomes part of the finished product. A problem is that the expansion and contraction properties of the resin and the inserted objects are not necessarily equal. Leaks or gaps can develop between the inserted object and the cooled plastic resin. This problem is amplified by the fact that plastic resin is known to shrink an appreciable amount as it cools. U.S. Pat. Nos. 3,364,292; 4,023,257; and 4,847,028; also discuss rotomolding with inserts added to the molded product. All of the above-cited references are incorporated herein by reference.
As noted in the above-cited prior art, rotomolding is well-suited for forming a plastic tank or reservoir structure. Such tanks are often used as hydraulic reservoirs for hydraulic systems, such as used in heavy machinery, including cranes, backhoes, demolition shears, bulldozers, and the like. In hydraulic systems, it is important to keep the hydraulic fluid free of debris. Consequently, filtering elements have been incorporated in the hydraulic systems to filter debris from the hydraulic fluid. Further, as set forth in U.S. Pat. Nos. 4,143,193 and 5,911,938 baffles are often incorporated into hydraulic reservoir tanks, as well as fuel tanks, to dampen the forces of moving liquid within the tank. The baffle designs suggested in these patents are integral with the finished tank. Further these designs increase the complexity of the mold, an increase in manufacturing time and expense.
It is an object of the present invention to provide a rotomolded hydraulic reservoir with an inserted baffle. It is a further object of the present invention to provide a rotomolded hydraulic reservoir with integral filter bowl having an extended integral filter enclosure with a coupling insert. It is another object of the present invention to provide a rotomolded hydraulic reservoir with a second fluid return. It is another object of the present invention to provide a hydraulic reservoir that is economically manufactured. It is a further object of the present invention to provide an effective, easily replaceable filter element for a hydraulic reservoir.
The above objects are achieved with a rotomolded hydraulic reservoir having an inserted baffle according to the present invention. The hydraulic reservoir is a one-piece tank structure. Specifically, the hydraulic reservoir includes a plastic container body defining a container cavity for receiving the hydraulic fluid. The insertable baffle is positioned in the container cavity through an access manway formed in the container body and is removable therefrom. The container body includes holding members for positioning and holding the baffle in place. A flange around the manway access may further include a baffle positioning mechanism, such as a pair of baffle receiving slots.
The removable baffle may be made of metal such as steel plate. The baffle may be held in place, in part, by opposed notches molded in the lower portion of the container body opposed from the manway access. The opposed notches may be formed as inwardly extending projections of the outer wall of the reservoir that are spaced to receive the baffle therebetween.
Several alternative modifications are possible with the inserted baffle design for the reservoir of the present invention. The holding members of the container body could be placed in a position extending from the sides of the reservoir, or may be offset from each other. The inserted baffle design of the present invention allows for a simple efficient mold construction while still allowing an efficient baffle to be easily positioned in and removed from the hydraulic reservoir.
The container body may form a filter cavity in fluid communication with the container cavity. A filter element coupling insert, such as a machined metallic bushing, may be molded in the container body adjacent the filter cavity. The insert defines an opening, specifically an internal bore, providing the communication between the container cavity and the filter cavity. A removable filter element is positioned within the filter cavity and coupled to the insert. The removable filter element seals to the exterior of the insert.
In order to help ensure a positive seal between the resin and the part to be included, the present invention generally provides a container body forming a filter cavity with an end having, in cross-section, a bowl-shape. The insert is positioned adjacent to the cross-sectional bowl-shape of the filter cavity. The bowl-shape offers controlled shrinkage tolerances in the general vicinity of the insert.
These and other advantages of the present invention will be clarified in the description of the preferred embodiments taken together with the attached drawings in which like reference numerals represent like elements throughout.